1. Field of the Invention
The present invention relates to brakes for a warping knitting machine having a main and a supplemental drive arrangement and, in particular, to a brake that operates upon interruption of a main power circuit.
2. Discussion of the Relevant Art
The invention concerns warp knitting machines of the type wherein a main shaft is driven by an electric motor and which also has at least one electrically driven arrangement exercising control over a thread feed. The thread feed is connected to the same electrical circuit as the main motor.
In known warp knitting machines of this type (DEOS No. 2214862) the additional arrangement has an electrical regulating motor for maintaining the revolutions of the warp beam at a constant and predetermined speed for providing a constant feed rate of yarn. For this purpose, the warp beam is driven by the output of a differential (interference) drive having one input connected with the main beam and the other input connected with a control motor. The control motor is itself controlled by a regulating arrangement which measures the present value of the thread feed speed and compares it with the desired value. It has already been suggested (German patent application No. P2904367) to employ, as an additional arrangement, an electromagnetic system for presetting a jacquard arrangement. In this case, every jacquard controlled guide cooperates with an electromagnet whose moveable core at a particular point in the machine cycle stops together with the controlled guide or leaves it free for further movement.
Heretofore, in the case of power failure, the electrically powered supplemental drive arrangements stop immediately while the main shaft, having a high speed and mass continues to rotate. This difference in deceleration occurs especially when the two systems are not mechanically linked. While continued rotation time is less than a second, when the machine is operating in the order of 1,600 to 2,000 revolutions per minute, this corresponds to approximately 20 courses. Thus a power break of less than a second, which occurs occasionally in modern power circuits and quite frequently in the power circuits of less developed countries, can lead to quite substantial faults in the ware. Thus, for example, when the warp beam is driven by means of a control motor, the warp beam will immediately be halted at power failure while the main shaft will continue to run. This means, in effect, that all of the warp threads will be torn. Also at the onset of a power failure, when the electromagnets of a jacquard arrangement no longer receive any more power, no patterning will occur. Thus, over a substantial portion of the goods, a clearly noticeable strip of improper patterning will be seen.
Also, a known knitting machine employs a main beam with an electrically activated brake. This brake, however, goes into its braking position on the application of power and merely serves to halt the main beam at a particular point in its cycle of rotation (U.S. Patent 2,779,448).